To optimize the thermodynamic cycle of gas turbine engines, especially under partial load conditions, heat exchangers are commonly used. Suitable heat exchange elements, such as heat exchange tubes of a tube matrix are disclosed in DE-PS 36 35 548, where the heat exchange tubes of the tube matrix are of U-shape. These tube matrixes are attached to ducts that serve as manifolds to supply compressed air to be heated and as collectors for the compressed air after it is heated.
Efforts to achieve compact connection of heat exchangers with gas turbines have heretofore encountered substantial difficulties in that the problem was not only to transfer deadweight loads and acceleration forces from the tube matrix to the engine, but also to minimize the development of loads from large temperature differences. Since the engine is intended for vehicular applications, a limited installation space is available which requires a space-saving construction not necessarily compatible with the requirement for low weight.
In a design disclosed in DE-PS 35 29 457 the heat exchanger casing is designed as a cantilevered load-bearing structure one end of which is secured to the turbine. In this arrangement the forces acting on the tube matrix, i.e. deadweight and the acceleration forces, are resisted by the heat exchanger casing. Relatively large expansion movements, especially when vertical acceleration forces act on the opposite end, are produced. This necessitates a correspondingly elaborate casing construction to achieve the requisite rigidity. This design carries a considerable weight penalty and does little to achieve a space-saving close attachment of the tube matrix to the turbine, for the reason that the bearing and casing configuration requires additional space between the tube matrix and the gas turbine.
A gas turbine with an attached heat exchanger has also been disclosed in U.S. Pat. No. 3,968,834, where a rigid frame envelopes the heat exchanger core to contain the core. Said frame in turn bears on the engine through a tubular rack. The heat exchanger core proper is suspended in the frame by means of two trunnions on opposite sides, with no provision to locate the core axially. A point transfer of heat exchanger loads to the frame produces peak stresses in the suspension members and, especially for vehicular applications, stress cracking in the heat exchanger. Ultimately, this particular arrangement of transfer of forces from the heat exchanger core through trunnions, frame, rack and bearing produces a rather elaborate design defeating the effort for an effective light-weight construction.